An assemblage of lizards from the early cretaceous of Japan

Abstract

The Early Cretaceous deposits of the Tetori Group of western Japan have yielded a diverse wetland vertebrate fauna including both aquatic and terrestrial components. The latter include several lizards, three of which have been named and described in detail: Kaganaias hakusanensis, a long-bodied aquatic lizard; Kuwajimalla kagaensis, a herbivorous borioteiioid; and Sakurasaurus shokawensis, a relative of the Chinese Jehol genus Yabeinosaurus. Here we describe lizard material from the Shiramine locality representing five or six additional taxa, three of which are named herein: a small lizard represented by two associations, but of unresolved phylogenetic position; a slightly larger lizard with tricuspid teeth that is related to borioteiioids; and a bizarre lizard with bicuspid teeth represented by a single, but morphologically unique, jaw. The three additional lizard morphotypes are unnamed. One has bicuspid teeth but unspecialised jaws. The second has small unicuspid teeth in a dentary bearing a deep coronoid process and resembling the dentary of the enigmatic Late Cretaceous Mongolian Myrmecodaptria microphagosa. The third morphotype is represented by a single fragmentary specimen and has small teeth in a deep jaw. Together, the Kuwajima lizards form a phylogenetically and morphologically diverse assemblage.